1. Technical Field
This invention relates to modification of pump designs for transferring liquids and to modification of compressor designs for transferring gases (the transferred fluid being in shear), to increase efficiency and reliability of the fluid transfer.
2. Discussion of the Prior Art
The state of the prior art for design of pumps and compressors have attained only limited efficiencies. Efficiency is usually defined to mean the ratio of the amount of energy stored in the pumped fluid to the energy put into the pump. Indicators of high efficiencies not only are less leakage, but higher output density and pressure. Gas fluid pumps, such as automotive turbochargers, have an efficiency typically of 50-60%, liquid pumps typically of 70-85% and some special automotive oil pumps of up to 90%. The limited efficiency of the prior art is indicative of leakage; an ideal pump or compressor would allow no leakage between the relatively moving parts therein which do the pumping. In addition, affinity or adhesion of the fluid to the pumping surfaces causes shear losses which result in heating of the fluid.
State of the art pumps or compressors incorporate a certain degree of intentional looseness between the relatively moving parts, such as a rotor and housing, to accommodate differential thermal expansion of the parts and to reduce the losses due to shear since the shear losses increase as the viscous film thickness decreases. Such expansion will (i) cause rubbing or mechanical contact (ii) increase friction between such parts, and (iii) increase friction as a result of surface viscous friction that arises between the moving parts due to fluid shear, if not alleviated by designed looseness. Such designed looseness thus limits efficiency.
There also exists in the prior art an inability to use lighter weight, lower strength metal materials (i.e. aluminum) for the compressor designs which experience high unit fluid loadings. Such loadings can distort such lower strength metals which thereby tend to exaggerate leakage or increase friction resulting in additional poor efficiency.